This application claims the priority benefit of Taiwan application serial no. 92109576, filed Apr. 24, 2003.
1. Field of Invention
The present invention relates to an active matrix organic light-emitting diode (AMOLED) and manufacturing method thereof. More particularly, the present invention relates to an active matrix organic light-emitting diode having organic thin film transistors (OTFT) therein to serve as active devices and a method of manufacturing the same.
2. Description of Related Art
Organic light-emitting diode is a highly efficient semiconductor device for converting electrical energy into optical energy. The device finds applications in many areas serving, for example, as light indicators or the light-emitting elements in a display panel. Because of some very special properties of the organic light-emitting diode such as wide viewing angle, ease of manufacture, low production cost, quick response, wide operating temperature and full coloration, it has been widely adopted in multimedia systems.
At present, active matrix organic light-emitting diode is one of the most rapidly developed display products. An active matrix organic light-emitting diode is fabricated by sequentially forming an anode layer, an organic light-emitting layer and a cathode over a substrate with an array of thin film transistors thereon. In other words, the driving devices for the active matrix organic light-emitting diode are thin film transistors.
In general, the semiconductor layer (the channel layer) of the thin film transistors within an active matrix organic light-emitting diode is fabricated using silicon material. Typically, the semiconductor layer is formed in a molecular epitaxial process. However, the cost of the equipment for fabricating a silicon semiconductor layer is high and the production period is long. In addition, it is difficult to form inorganic thin film transistors on a plastic substrate (a flexible substrate) because inorganic silicon has poor plasticity (besides, the plastic substrate has low endurance for high temperature). Consequently, the scope of development for the organic light-emitting diode is somewhat restricted.
Accordingly, one object of the present invention is to provide an active matrix organic light-emitting diode and manufacturing method thereof capable of reducing production cost and cycle time and yet permitting a higher processing temperature.
A second object of this invention is to provide an active matrix organic light-emitting diode and manufacturing method thereof that can be fabricated on a plastic substrate with fewer processing steps.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an active matrix organic light-emitting diode. Each active organic light-emitting diode comprises a thin film transistor, an anode layer, an organic layer and a cathode layer. The thin film transistor is formed on a substrate. The thin film transistor furthermore comprises a gate, a source and a drain. The anode layer is positioned over the substrate. The anode layer and the source terminal of the thin film transistor are electrically connected. The organic layer is positioned over the substrate covering the thin film transistor and the anode layer. The organic layer is an organic semiconductor material layer with light emitting capacity. The organic layer between the source and the drain also serves as a channel region for the thin film transistor. The cathode layer is positioned over the organic layer, thereby forming an active organic light-emitting diode. The organic layer between the cathode layer and the anode layer constitutes a light-emitting region. In addition, the organic layer is fabricated using long chain organic polymer material such that the organic molecules are aligned in a direction parallel to the source-to-drain direction but perpendicular to the anode-to-cathode direction.
This invention also provides a method of fabricating an active matrix organic light-emitting diode. First, a thin film transistor is formed on a substrate. The thin film transistor has a gate, a source and a drain. Thereafter, an anode layer is formed over the substrate. The anode layer and the source terminal of the thin film transistor are electrically connected. An organic layer is formed over the substrate globally to cover the anode layer and the thin film transistor. The organic layer is a light-emitting organic semiconductor material layer and the organic layer in the area between the source and the drain serves as a channel region for the thin film transistor. A cathode layer is formed over the organic layer to produce an active organic light-emitting diode. The organic layer between the cathode layer and the anode layer constitutes a light-emitting region. In addition, the organic layer is fabricated using long chain organic polymer material such that the organic molecules are aligned in a direction parallel to the source-to-drain direction but perpendicular to the anode-to-cathode direction.
In this invention, the molecules within the organic layer are aligned along an axis parallel to the source-to-drain direction and perpendicular to the anode-to-cathode direction. Hence, the same type of organic material can be used to fabricate the channel of the thin film transistor and the organic light-emitting layer of the organic light-emitting diode.
In addition, the organic thin film transistor is used as an active device in the organic light-emitting diode in this invention. Because the organic thin film transistor is easier to fabricate compared with a conventional inorganic transistor and the same type of organic material is used to fabricate the channel of the thin film transistor and the organic light-emitting layer of the organic light-emitting diode, the active matrix organic light-emitting diode is easier and cheaper to produce.
Furthermore, with the organic thin film transistor serving as the active device of an organic light-emitting diode, the required processing temperature is lower and the organic layer has greater plasticity. Therefore, aside from being fabricated on a glass substrate, the organic light-emitting diode of this invention can also be fabricated on a plastic substrate (a soft substrate). In other words, the fabricating method has a wider range of applications.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.